NPC 15669-modulated human polymorphonuclear neutrophil functional responsiveness: effects on receptor-coupled signal transduction.

Abstract

1. The effect of NPC 15669, N-carboxy-L-leucine, N-[(2,7-dimethylfluoren-9-yl)methyl]ester), an inhibitor of human polymorphonuclear neutrophil (PMN) adhesion, on granule exocytosis and the oxidative burst was investigated in PMN activated with receptor-specific pathophysiological stimuli. 2. NPC 15669 caused a concentration-dependent (1-30 microM) inhibition of the extracellular release of azurophil (myeloperoxidase) and specific (vitamin B12-binding protein) granule constitutents from PMN exposed to N-formyl-methionyl-leucyl-phenylalanine (FMLP), leukotriene B4 (LTB4), platelet activating factor (PAF), C5a and interleukin-8 (IL-8). 3. The receptor agonist-triggered PMN oxidative burst, measured as superoxide anion (O2-) production, was suppressed by NPC 15669. 4. Phorbol myristate acetate (PMA)-stimulated degranulation and O2-) production were unaffected by NPC 15669. 5. NPC 15669 (0.1-10 microM) inhibited receptor-triggered inositol 1,4,5-trisphosphate (IP3) production and the IP3-triggered increase in cytosolic-free calcium ([Ca2+]i) in FMLP-activated PMN, but not in cells exposed to the other receptor agonists. 6. NPC 15669 suppressed FMLP but not PMA-stimulated redistribution of protein kinase C (PKC) in PMN. 7. The specific binding of [3H]-FMLP but not [125I]-C5a to PMN was inhibited by NPC 15669. 8. NPC 15669 suppressed O2- production and the rise in [Ca2+]i in PMN treated with the guanine nucleotide-binding protein (G-protein) activators, sodium fluoride (NaF) and mastoparan, respectively. 9. The results show that NPC 15669 inhibits PMN responsiveness to various receptor agonists, and suggest interference with receptor-coupled signal transduction in this inflammatory cell at both the receptor and post-receptor level in a stimulus-specific manner.